In many parasitic diseases large amounts of parasite antigens and corresponding antibody result in circulating immune complexes. A Clq ELISA has been developed whereby Clq was adsorbed to polystyrene microtiter plates and the complexes bound to Clq from serum were detected by peroxidase labeled anti-human IgG. The sensitivity of the ELISA for detecting immune complexes in sera from filarisis patients was enhanced by the addition of polyethylene glycol to the assay system. Antigens and antibody have been labeled with peroxidase for use in detecting specific antigens and antibody in sera from patients with parasitic infections.